Page 408 - Basic Electrical Engineering

or,

Magnitude of the in-phase current, i.e., the current which is in phase with the
voltage, I = I cos ϕ, is
L

I I cos ϕ = 20.57 × 0.438 = 9A
L
L

This is the minimum current drawn by the circuit and is called the resonant
current, I .
0

Example 3.42 An inductor having a resistance of 4 Ω and an inductance of

20 mH are connected across a 230 V, 50 Hz supply. What value of
capacitance should be connected in parallel to the inductor to produce a
resonance condition? What will be the value of the resonant current?

Solution:

For resonance, the current drawn by the capacitor in parallel must be equal to

I sin ϕ .
L
L